


Devil's Flesh and Bones

by EvilOfEden



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - Demons, Alternate Universe - Urban Fantasy, Blood and Gore, Demon!Byleth - Freeform, F/M, Other, Other Additional Tags to Be Added, Religious Guilt, Slow Burn, demon hunter!Seteth, post-black eagles route...?, trans!byleth
Language: English
Status: In-Progress
Published: 2019-10-31
Updated: 2019-10-31
Packaged: 2021-01-15 06:40:03
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 4,960
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21249065
Author URL: https://archiveofourown.org/users/EvilOfEden/pseuds/EvilOfEden
Summary: Jeralt is missing. The only clue is Byleth, a young demon whose antiquated memories are spotty at best.Seteth wants nothing to do with this. But in order to save himself and those he loves, he'll have to break his own rules, make a pact, and risk turning into a demon himself...again.





	Devil's Flesh and Bones

_“Seteth. If you’re reading this, I’ve already passed…”_

The headlights did not illuminate a house, but an abandoned cornerstore already half-collapsed on itself in the middle of the woods outside of Remire. Even from across the road, it reeked of sulfur and rotting meat. Seteth checked the coordinates of the text one more time. His phone reminded him that it was out of service, and almost out of battery.

An inquisitor’s work was never done. Especially when the cryptic message came from Jeralt, lost leader of the Inquisitors and Rhea’s right-hand man. Her face had lit up when she heard who the text was from, and crumpled oh so subtly into that pursed frown after reading it. Seteth had driven out immediately at her request, paperwork be damned. He’d barely had time to call Flayn and tell her to look forward to another late, late night.

Lights flashed inside. Seteth grabbed the collapsible lance and his trusty mace from the trunk before heading inside. Other inquisitors preferred more modern weapons, but demons took no more damage from a bullet than a blade, and Seteth could never shake the need to be in the thick of combat. Fog had already surrounded the premises, prepared to blot out any bloodshed until midday tomorrow. 

Despite the stench, the store itself presented a picture of peace. Not much dust had settled on the shelves, and someone had left the TV on in the corner. It flickered between static and lottery numbers. Counters were half-stocked with cheap snacks and old magazines, nothing so stale or ancient to suggest this tiny slice of urbanity had been abandoned for more than a week. Yet it smelled worse than the possessed butcher he and Catherine had tracked down a few years back, a stench that suggested corpses and demons in equal measure.

Seteth found a flashlight among the cheap tools for sale, and after a moment’s thought, left a handful of loose change on the counter in case anyone returned. The Jeralt he’d known never would’ve lived here. This was the sort of place one brought themselves to languish and die in without inconveniencing anyone.

Dust motes trailed from the ceiling and danced in the flashlight’s glare. Someone had knocked over a carton of cigarettes behind the counter and rifled through the contents. Packaging discarded near the freezers, some of them still damp from thawed meat. Not enough to explain the scent, but something was still here…and feeding. Or, noting the lack of claw marks that suggested a more precise touch, was being fed.

Jeralt wouldn’t…

A crackle of static. Snatches of a radio, too out of range to come in clearly. An unfamiliar voice swore and was followed by the sound of boxes falling over, which led to more swearing. There in the back was a hallway leading to a pair of restrooms, and next to them, an unmarked door. It smelled less of rot back here, but intermingled with sulfur was the stench of cheap cigarettes.

Flashlight off, Seteth crept toward the door with only the light of the old TV and vending machines to guide him. Considering the size of this store, the room was probably too small for a lance to be effective; he settled a hand on the hilt of his mace. It was an old hunk of equipment, iron inlaid with silver, with more nicks in its metal than Seteth bore scars, but it had saved his skin more times than he could count during his tenure as inquisitor.

He paused outside the door. The radio had finally lapsed onto a station with bawdy classic rock loud enough to break free from most of the static. The unfamiliar voice sang along to lecherous lyrics about making love in the back of a car after midnight. That voice was…not unpleasant, aside from the subject matter.

Oh well. No one could ignore that telltale demonic scent, and anyone who didn’t report it was likely a collaborator. Seteth at least let the chorus finish before he kicked the door in.

“By order of the Church of Seiros, I order you to freeze.”

No one could’ve mistaken the woman sitting on the table for anything other than a demon. But for Seteth, it wasn’t the horns or wings that tipped him off, nor whiplike tail or the smoke-colored scales that ran up her limbs before fading into more mortal flesh. What bore into him instead were the smaller details—the pointed ears, the nails that grew into claws far too quickly, the maw full of fangs that wouldn’t look out of place on a beast. These same marks taunted him from the mirror, the shameful reminders the goddess had demanded he keep.

The demon put her clawed hands up. Dark, glowing eyes examined the inquisitor with a raised brow. “Freeze? I’m afraid playing cool isn’t my forte when I’m so…smokin’.” Her delivery was dry enough to border on sarcastic, even when she summoned a lick of flame to dance across her fingertips, and her wink didn’t match her otherwise expressionless face. Seteth kept his hand on his mace. The demon sighed after a long moment. “Knew that was a dumb pickup line. Are all members of the church such killjoys? No wonder Jeralt left.”

“Where is Jeralt?” Seteth asked. Not in this room, surely. It was a boiler room, its head almost stifling, but someone—likely this demon—had turned it into a break room of sorts. Cheap fold-out furniture scattered the area, covered in gossip magazines and discarded cigarettes. Some of the celebrity faces were burned through, others circled with pens and snide commentary. No food or drink—if anything, the rotting stench was almost absent here.

The demon shrugged. “Don’t know, but if you’re the backup he was talking about, it’s taken you long enough. I’ve been trapped here three whole days. Read these mags back to front and back again. I’m so bored, I’m even sick of mastur—”

Seteth sighed through his nose as he brandished his mace and pointed it at the demon. “Jeralt’s text claimed it would only send in the case of his demise, and it included coordinates to here. It said nothing about you. Now, if you do not wish for a prompt exorcism…”

The demon’s brows scrunched together, almost obscured by her dark teal bangs. “Of course he’s playing dead. Would you pay attention to anything less? And if he mentioned me, I’m sure a whole slew of exorcists would’ve shown, no matter how tame he claimed I was. No kill like overkill, right?” She hopped off the table and strode right up to Seteth, gazing up at him with her arms crossed and her tail wrapped loosely around her legs. “Well then. Are you ready?”

Seteth normally knew better than to talk with demons. The Church of Seiros wasn’t exactly a “smite first, ask questions later” sort of group, but there were usually summoners or other witnesses to consult instead of asking a demon itself. They were the sort to twist words so that truth and lie intermingled, and an innocuous question could sign away one’s soul. But this demon was his only lead beyond Jeralt’s cryptic message, and of all people to lead Seteth back into a trap of temptation, Jeralt was close to the bottom of culprits on that list. 

Besides, this demon was still mostly human in appearance. Either she had yet to succumb to the full power of a pact, or she had escaped a more monstrous form through the redemptive powers of the Goddess, and crawled toward a human life once more, just like…

“Ready for what?”

“To smite the actual feral demon lurking around here, of course. Or did Jeralt leave that out of his message too?”

Before Seteth had time to react, the demon was suddenly pressed against him—how did she pass the range for his mace so quickly?—to search through his pockets. She pulled out his phone and, still chest-to-chest against him, opened it to search the messages.

“I knew the church was old fashioned, but a flip phone? Really?”

“What do you think you’re—” Seteth tried to grab his phone back from the demon, who he decided absolutely had to be a succubus. She certainly had the body for it, despite the horns and scales. Even the brief contact had his skin flushing red, and he hadn’t practiced temperance all these years to become so easily flustered. She winked as if to prove his theory true as she flapped out of the way, wings keeping her a few inches above the table as she scrolled through the texts. He reminded himself to focus on her inhuman features, focus on anger and disgust instead of…

“Huh. Just coordinates. Typical cagey Jeralt.” The demon tossed the phone back to Seteth. Seeing as he still had his mace in one hand, he wasn’t the most graceful when catching it. The demon smirked a little at the sight.

“You mentioned another demon,” Seteth said once he’d finally returned both the phone and the mace to their proper places, keeping his hands free in case this demon tried to invade his space again.

She nodded toward the back of the building. “Jeralt chased off some thieves last week, but one had made a pact for power, and it nearly broke when his mission failed. So we locked him up in the basement, and I tossed some snacks his way to keep him occupied while Jeralt figured out a way to break the pact. Except…then he had to leave on urgent business, said he’d call for help, and not two hours after he left, the thief completely turned. And since he remembers I fed him…he keeps coming back for more. Except now he wants to eat me. At least Jeralt set up wards in this room…”

Seteth glanced at the walls of the room, but whatever blessings were upon them remained invisible to his gaze. Did he still have to worry about wards? Clearly not, if he’d made it into this room without being bound to where he stood. Unless Jeralt had included his name in a loophole, as he must’ve with this…whatever she was to Jeralt. A captive? A project? A…kindred spirit, somehow?

“So you’ve been waiting here, locked alone in this room, because you cannot fight this demon alone and Jeralt left you here.”

The demon bit her lip, beads of blood trailing behind one sharp canine. “I mean. I’m sure I could, if I wanted. But Jeralt says I haven’t…recovered.”

He knew better than to ask. “Recovered from what?”

“Don’t remember. Something to do with my last pact. Burnt up my body and mind like one of these.” She picked up a cigarette, small and frail in claws she didn’t bother to hide. Flames briefly engulfed her grasp, and soon, all that was left were ashes the color of her scales, and a haze intermingling with her sulfur.

The ground rumbled. Something groaned, sounding as if the earth itself were pulling itself apart down below. A more human scream followed.

“Sounds like the beast has found prey. I must make sure it hunts no longer.” Seteth prayed under his breath that the goddess would see him through once more. After all, if not for her grace, he’d be the one being hunted. His few remaining fangs felt as if they were crowding his mouth.

“If you’re really going to kill it, you’ll hear no complaints from me.” Finally landing on the ground again, the singing demon looked up to Seteth and said, “Forgot to introduce myself. My name’s Byleth. Mind keeping that beastie from making a meal out of me, if I show you where it’s hiding?”

Seteth knew better than to make a pact over something so innocuous. But he walked on, and she directed him with no promises made, and that was enough of a loophole for him.

* * *

The river outside had once been idyllic. Sunlight had dappled through the shadows of leaves to make the clear waters glisten. Children had played along the banks, chasing after fish and digging small homes for crawdads. The occasional tourist tried to raft down in an innertube and got stuck; Jeralt had always waded out to help when that happened, laughing in his good-natured way about it afterwards with his regulars. At night, he and Byleth would fish from the deck, and he’d tell stories about his adventures as an inquisitor.

Even in this short time, the demon downstairs—the Black Beast, she’d taken to calling it—had left a mark on the shore. The foliage was blush with bright red pustules, curling in on themselves as their fruit grew rotten and sloughed off their flesh into the now-murky waters. People didn’t come around any more. Byleth didn’t know how many had been eaten. She’d kept out of the way of humans, but she still didn’t want to look at the corpses in case she recognized them.

“We were going to replace the stairs in a couple weeks,” she told Seteth as they passed under the rickety wood of the deck. Byleth didn’t understand this urge to explain anything to the green-haired Inquisitor, but her mouth rattled anyway. “Here, let me get the light. Don’t want to keep track of a flashlight during battle.” Click. The riverbank and the slowly collapsing store were illuminated in a deep orange glow, the color of dying embers.

Just under the stairs were the doors to the cellar. Jeralt didn’t hunt demons anymore, but his old tools and traps rested under the humble store, waiting to be used again. Byleth knew how to use half of them, and how to avoid the remainder. She’d always asked Jeralt why he was so keen on keeping her alive when her kind were his mortal enemy.

“I’m already a heretic,” he’d said once, “so no harm in me saying that I don’t think every demon is actually all that bad. Just like we humans aren’t all good.” He’d ruffled her hair after that and changed the subject, as he always did. For a man she’d spent almost twenty years with, she knew pitifully little about Jeralt.

This so-called backup, though? He was intriguing. Not just howhis rigid poise and stern gaze differed from all the other humans who’d come and gone through the corner store she and Jeralt had called home. There was something about him that Byleth dared call familiar. Was it something in his face? The faintest scent of brimstone buried under cedar and pine? The hint of fangs that crept out when he grit his teeth?

Whatever it was, this man wasn’t entirely human himself. Byleth certainly felt more kinship with him than the rotting husk of a beast waiting downstairs. 

“Judging by the tracks,” Seteth said, “this demon seems to be quadrupedal. Yet its front paws still seem to possess thumbs…it could use tools, or grapple someone before eating them.” He didn’t ask for confirmation, but did glance at Byleth to gauge her reaction.

She shrugged. “Haven’t seen much of it past the first night. I threw a couple fireballs at it to scare it off, but any more and I might’ve burnt the place down—then I’d have nowhere to hide.”

“…Prudence is technically a virtue,” Seteth noted. “Which is why we won’t charge in like hooligans if I can help it. Are there any other entrances? Or windows, perhaps?”

“No, unless you want to make a hole in the floor overhead. Got a sanctified jackhammer or something?”

Seteth shook his head, but his gazed stayed on Byleth. Not that this was uncommon. Even when she had a more human glamour in place, she attracted stares. Perhaps it was her natural charm, or the revealing clothing she wore no matter what Jeralt put in her closet. Except Seteth seemed to be looking up more than folks tended to—at her wings, specifically.

“Can this beast fly, or leap particularly high?”

Oh no. Byleth could already tell where this was going.

“It’s got strong enough legs, but I haven’t seen it jump. Other than when it walks, it still tries to move like it’s…human.”

Seteth grimaced at that. “Then there may be some hope for him, and for us. Now, I think—”

“If you want me to play bait for that thing so you can surprise it, think again.” Byleth crossed her arms in a huff, like she’d seen the actors do on late-night TV when Jeralt was asleep. “Unless, of course, you’re willing to make a deal?”

“I don’t bargain with demons,” Seteth repeated for the umpteenth time, as if trying to convince himself of the fact. “But seeing as this is your home, and it appears I am the sole person answering Jeralt’s call, perhaps it would behoove you to cooperate.”

“And how do I know you won’t let the Black Beast eat me before you kill it, and get rid of both of us at once?”

“Believe me, that’s the one temptation you’ve almost led me to. Congratulations.” They held that standoff-stare for a solid minute, but Seteth crumpled with a sigh under Byleth’s naturally cold gaze. “Listen. You’re the only lead we have on Jeralt, what’s happened to him, and why he abandoned the church. I am not in the position to offer anything to you, but should you answer our questions, the church may be willing to allow you to live in return.” He turned toward the stairs. “And, should you wish it, they can offer you redemption too.”

Aha. “So you’re also a demon, aren’t you?”

Seteth glanced at her over his shoulder. While the rest of him remained composed, his pupils had narrowed into predatory slits.

“I was. But for the grace of the Goddess and the guidance of Seiros, I am no longer a beast.” He smiled, but it was hard to tell if it was welcoming or a threat when he showed his fangs. “If nothing else, you will find it a far less lonely life to lead.”

Leaving her to decide on her own, Seteth bound up the rickety stairs two steps at a time. This time, he prepared his spear.

* * *

It had been years since Seteth had wings. He tried to convince himself that he had no memory what they’d felt like. He’d cast them aside with the rest of his demonic form when he’d given himself up to the church, and his only reminders should’ve been the scars that ran down his back.

But even deep in the woods, where it was so dark that the sky and the silhouettes of trees melded into one, standing up on the deck with the wind in his hair made him want to take flight. He cursed the phantom sensation of those bones and tightened his grip on his lance, extended and locked into place. Down below, Byleth saw reason at last and darted to and fro around the door. Even from here, Seteth could smell the cocktail mixture of brimstone, cigarettes, and cheap perfume. Surely, the Black Beast noticed the same. Vice spoke to vice, and they were sinners one and all.

The cellar doors broke open. Seteth obeyed his body’s instinct to jump and aimed the lance down. He struck the Black Beast between its shoulder blades, narrowly avoiding the spikes on its back, and blood splattered his hands. The demon howled, bestial screams wrapped around a pained mortal voice. The night lit up as Byleth lobbed fireballs into the Black Beast’s open maw.

The Black Beast reared back. Seteth leaped off before the beast could knock him off, rolling as he hit the ground and rising with lance ready. He found the cellar door flying toward him, ripped from its hinges by the demon’s strength. He barely had time to duck. The door clipped Byleth’s foot; she swore and accidentally dipped into the enemy demon’s range. It prepared to pounce. Seteth ran toward its blind spot to slash it with the lance.

But the beast turned too quickly and caught the lance in one clawed hand. The tip of the spear dug into its palm, its writhing black skin like so many snakes leaking through the wound. Seteth supposed he must’ve looked the same, once. It pulled him in before he could let go of his weapon and wrapped its other hand around him, as if he were a toy. Seteth shoved at the claws even as they constricted. Bones began to snap in protest.

“Seteth!” Another fireball flew at the Black Beast, but no pain flickered in its eyes, so red yet so cold. 

It would be easy, he distantly thought, to escape this. Even ordinary civilians still whispered rumors about The Gargoyle of the Rhodos Coast, even with the church hiding how many sunken ships and missing people had been found in his old lair. All he had to do was tap into that strength…

(No. He cannot become a monster again, lose Flayn again, forsake his memories for the feeling of blood on his tongue and under his nails.)

Perhaps the Black Beast knew what power lay in its grasp. It was just as likely base hunger that brought its teeth crashing through Seteth’s ribs and piercing through his lungs. His breath stopped short. The world froze for the brief second when a tongue lapped at his heart before yanking it out with a chorus of snapping blood vessels. Without air, Seteth couldn’t even scream. The demon let him tumble out of its hand, a ruined ragdoll.

He’d promised himself so many times that it was better to die a man than live a demon. Yet as he fell, his mind scrambled with animal fury for any chance at survival. Would bringing back wings and scales save him? Could he suck out someone’s life again and live to remember it this time? 

The wind shifted direction against his face, taunting him with all the air it denied his lungs. He was terrified he’d succeeded in his moment of weakness. Then his brain caught up to his ears and filled with Byleth’s terrified reprimands. The passive mask had finally melted away into anger and panic.

“Goddess damn every last inch of this—are you still there? Can you talk?” Were those…tears?

Pain and cold raced through him to see which could spread faster. Each breath came more sharp and shallow than the last. “I…yes.”

“Good. Then there’s still time.” 

Byleth set him down on the top of the roof. The tile on his back shouldn’t have felt so rough when his chest was literally caved in around his lungs. He might’ve laughed, if he’d had the breath to spare.

Words spilled out of Byleth’s mouth. “Listen. I can save you. I have enough power for that. I can make it so none of this happened to you. But I can’t do it unless we make a pact.” she offered a hand. “As long as you can say your name—”

Seteth slapped the demon’s hand away as if merely having it near would make his own skin sluice away. “No.”

“Then you’re going to die, that bastard down there’s going to eat your corpse, and then it’ll eat me!”

“So be it.” Seteth shut his eyes and focused on the cold building inside him before the warmth of temptation could pull him back in. If the Goddess could reach down her hand instead…

“If we’re both dead, who’s going to tell Flayn?”

If he’d still had a heart, it would’ve stuttered.

“That’s right, I read your texts with her. She’s special to you, right? If the both of us die here, in the middle of nowhere, how’s she going to know? Won’t be until this beast causes a massacre, who knows how many die trying to stop it, and then some hapless sap runs into your corpse up here. Are you going to risk letting her see that? Letting this be the last image of you burned in her brain?”

The image of the goddess was replaced by that of his daughter, reaching down to touch cold dead skin and weeping. She’d pray and pray until she went hoarse, and then someone like Alois would have to pull her away. Would she kick and scream and run back until she couldn’t fight it anymore, or would she be resigned to an even lonelier life than before?

Byleth grabbed Seteth’s hand and pressed it against her chest, warm and soft with the pulse of life. “I, the Ashen Demon Byleth, bind your life to mine. So long as one of us stands, the other shall not falter. My heart shall be yours, and in exchange, you shall guard me with all your strength. May Hell reclaim us only if we break this pact. Do you swear?”

Goddess, forgive him this weakness, but his first promise had been to never abandon his daughter again. 

“I, Seteth…” Somehow, his own name felt wrong on his tongue. He didn’t know why. It was all he’d ever called himself. Yet he found himself correcting, “I, Cichol, agree to your pact.”

His life

flashed before

his eyes

backwards

and he found himself standing on the edge of the roof again. The door below was whole. So was his chest. Cool evening air dragged its crisp nails down his throat with each breath, but it was breath all the same. His heart beat far too quickly, far too warm. For it was no longer his heart, was it?

The basement door broke open. But this time, Byleth laughed as she lobbed fire at the Black Beast, and her hair was alight with glowing green. She caught Seteth staring and winked. This was neither illusion nor dream.

Once more, Seteth vaulted off the roof. With a demon’s blood flowing through his veins once more, newfound strength carried him farther. His spear pierced into the Black Beast’s skull, and through, blood and black bile soaking into his boots as the skull crumpled under his soles. It was…exhilarating. He lied that what bubbled in his chest was a mix of vengeance and adrenaline, nothing more.

The beast dissolved under him, darkness melding back into the shadows of the oncoming night. Seteth found his lance embedded in a human skull, hair almost as red as the blood. The inquisitor ran his tongue along his teeth and let the taste of his own blood stave him off as he stepped off the body and searched the dying man’s pockets. After all, he could no longer tell the man’s identity from that ruined face.

“This is the part where most humans would be puking,” Byleth said. A faint green glow clung to her teal hair.

“I have had a few years to become accustomed to such sights.” Seteth found a wallet and flipped it open. A few dollars, stolen cards that each bore a different name…ah, there was an expired ID. Miklan Gautier. Curious…far as Seteth had heard, that was a more well-to-do family from up north near Sreng. How did one of their sons end up here, a disheveled thief turned demon in a near-forgotten town?

Questions for later. Right now, he had more personal concerns. He stepped into the light and pulled open his shirt. He found untouched skin, decorated by a dusting of green body hair and the white traces of old scars. They were now joined by a mark over his chest, a symmetrical and abstract piece that somehow reminded him of a winged figure.

“We truly did make a pact,” Seteth muttered. His hands absently buttoned his shirt back up and then ran along the skin of his arms. Still flesh. Good. He hadn’t cast aside everything in that one moment of weakness.

“We did. That’s my heart, beating in your chest.” As if to prove this, Byleth grabbed one of Seteth’s hands and pressed it against her chest, right over the line of her corset. Her skin was warm, but true to her word, he felt nothing. “We’ve got to stick together now, if we don’t want to die. Or become as this idiot here.” The demon nudged her deceased foe with her foot. “Guess that’s one way to be certain he won’t come after us, huh?”

“…Yes. No magic could return someone from that, no matter how diabolical.” And cool at it was outside, the stench of death was already attracting flies. “Help me find a tarp or something to cover him with. Then pack your things while I make a few calls. We’ll leave once I do—I would rather not explain you to the Remire police.”

“Of course. Jeralt left the motorcycle, that should have a tarp…” If Byleth was bothered by the corpse, it didn’t show on her face. It was so impassive, Seteth almost wondered if he’d imagined her panic on the rooftop. Or had that been a show to sway him?

Once the tarp was found and the body given a final semblance of decency, Byleth sprinted toward the door inside to pack her things. She paused in the entryway and called out, “Where are we going, anyway? Garreg Mach?”

Seteth paused in the middle of entering Rhea’s number into his dying phone. “Why there? It has been abandoned for centuries.” He gave her time to voice her idea, but she stared at him blankly. Not at all unnerving, no. “We are headed to Enbarr, the capital of Fodlan. Have you been there before?”

Her face remained blank. Yet he swore her voice trembled ever so slightly when she answered, “No. I’ve never set foot there.”

**Author's Note:**

> Despite my best efforts, this idea would not leave me alone. I love Seteth too much and need to dump all the angst onto his lap.
> 
> That being said, I'm an author with two original novels in progress and a full-time day job, so updates may be sporadic (if at all). That being said, this is fun to write AND may help with some other projects I'm working on, so...fingers crossed.
> 
> Also, props to my dastardly beta reader, who doesn't even go here but read this anyway.


End file.
